Étude de matériels pour le controle d'un bassin

Ingénieur à la Compagnie des Compteurs.

Résumé

In order to keep track of river basin water resources and to keep pollution in check, each basin requires a central measurement network automatically collecting and transmitting the data and extracting the most important information therefrom. In other words, such a system could take the form of a central automatic data-collection and abstracting station transmitting by various links to satellite stations at strategic points in the basin and with the latter collecting data from local instruments. The report lists the main points of the study, i.e. a review of the values to be checked and necessary means of measurement, the setting-up of a local collecting station and its link with the abstracting station. A special study on stage measurement is in progress. Water resources : Stage and precipitation are considered of capital importance in this respect. Pollution: water temperature, conductivity, pH value and dissolved oxygen are the most important factors here, followed by turbidity, chlorides, nitrates, fluorides and precipitation. Environmental factors also need considering, i.e. air temperature, sunshine, wind velocity and atmospheric pressure. This has led to the author's distinction between "bi-measurements" and "polymeasurements" between permanent and mobile stations, which latter are installed temporarily for detailed analysis of a limited area. The rate of measurement should be the same for all the quantities measured, but leaving a margin of choice. More frequent measurements can be carried out on important rivers if required, i.e. of stage and precipitation for flood control purposes. Stage measurement accuracy aimed at is to within 0.5 cm to 1 cm for levels around 1 metre, and to within 3 cm to 5 cm if around 20 metres. A local station should be designed to accommodate different types of pick-up, though they should preferably be of an existing type ; signal adaptation means are therefore provided for. Three alternative forms of information delivery are provided for : 1) local perforated or magnetic tape storage and collection at periodic intervals ; 2) automatic hourly transmission by conventional telephone or wireless ; and 3) automatic cyclic calls for information controlled tram the main abstracting station. A station designed for a variety of uses is of modular construction, comprising direct or converted signal input units, a programmer reading the measurements, data storage, a logical output system extracting the data from storage and coding them up for transmission or local recording. Some forms of station can dispense with storage and dating functions, which are incorporated into the central station instead (if of the type periodically calling up the satellites. Other forms of station, however, will require all the necessary functions to allow completely independent operation for at least a month (power supply, dating and recording of information). The final item referred to in this paper is a special technological study on a stage measurement method in which the maximum stage to be measured is divided up into a number of sections each corresponding to a particular gas supply nozzle, with continuous stage measurement along each section by a manometer. The result is thus the sum of two terms, i.e. the number of sections under water and the manometer reading. This "Vernier" system gives accurate results over the full stage range.